In general, orthodontic therapy is to straighten crooked teeth by bonding brackets to the teeth and placing and ligating an archwire to slots of the brackets, wherein the teeth are corrected by retracting the teeth using a restoring force of the archwire or controlling torque of the archwire.
A method for retracting six anterior teeth usually employs a loop technique or a sliding technique.
The loop technique includes bending a portion of an archwire to form loops, ligating the archwire to brackets, and anchoring the hooks to the brackets by a ligating wire to produce a retraction force.
FIG. 1 is a view illustrating a process of forming a loop according to the related art.
Referring to FIG. 1, a loop 1′ is formed by bending a portion of a wire 1 using a tool. If necessary, a wire hook 2 may be mounted to a portion of the wire beside the loop 1′.
And then, as illustrated in FIGS. 2A, 2B and 2C, the wire is ligated to brackets 4 bonded to patient's teeth.
Finally, the hook 2 is ligated to the brackets by other ligating wire 3.
FIG. 2A shows an early stage before the loop 1′ starts activation, and FIG. 2B shows an advanced stage in which retraction of the teeth is completed.
If the activation is completed, the loop 1′ is supposed to be disposed at a center of both brackets. Actually, if the teeth are retracted by about 2 mm, the hook 2 abuts against the bracket 4, so that the hook is not further retracted. As a result, the hook 2 already mounted should be removed from the wire, and a new hook should be mounted onto the wire beside the loop.
FIG. 2C shows a new stage in which activation starts again after the hook 2 is mounted onto the wire.
The wire hook 2 is commonly used even in the case of retracting the teeth by the sliding technique.
The sliding technique includes ligating an orthodontic archwire to brackets and linking a closed coil spring or an elastic power chain to a hook to produce a retraction force.
FIG. 3 shows a process of mounting a wire hook according to the related art.
Referring to FIG. 3, a hook 2 is mounted to a proper location of the archwire 1, and a closed coil spring is linked to the hook 2 to produce a traction force.
Since the hook is mounted to the archwire by hands, the degree of precision is lowered. In particular, since a lower end of the hook is fastened to the wire, there is a drawback in that a volume of the archwire is significantly increased.
In particular, the above drawback is remarkable in the case of lingual orthodontic treatment in which a space is limited.